(1) Field of the Invention
The present invention relates to a semiconductor memory device, and more particularly, to the enlargement of a boundary-free semiconductor memory device (hereinafter, referred to as a slide access memory) in which data in two-dimensional memory cells including data in a memory cell designated by an address signal is accessed.
The semiconductor memory device according to the present invention can be used in multi-dimensional data processing such as video data processing.
(2) Description of the Related Art
In video data processing or the like, a video memory device is used for storing video data, and such a device often stores video data in correspondence with pictures displayed in a graphic display or the like. For video data between adjacent addresses stored in such a device, data processing or dust removing processing such as compression processing, difference processing, smoothing processing, and the like are often carried out, and for such processing in addition to access to a desired memory cell, it is necessary to access data in memory cells at the periphery of the desired memory cell. Therefore, in a video memory or the like a prompt access to memory cells at the periphery of a desired memory cell, as well as the memory cell per se, is required.
Also, the above-mentioned requirement is applied to processing for accessing every word unit such as a matrix calculation and three-dimensional data processing, as well as processing for accessing every memory cell unit. The efficiency of this type of processing is improved by providing a function for promptly reading stored data of adjacent addresses.
For this purpose, the applicant has already suggested a boundary-free semiconductor memory device (slide access memory) in which the rectangular shape of accessed bits can be easily reduced or enlarged, and the large capacity and high integration of the device are not affected (see U.S. Pat. No. 811,297).
When a memory system is extended by using a plurality of the above-mentioned slide access memories, the same rectangular group of bits, such as 4.times.4 bits, are accessed for each slide access memory, and thereafter, only the 4.times.4 bits including a pointing bit PB are valid and the other bits are invalid. For this purpose, a boundary-free semiconductor memory device including a plurality of slide access memories may be considered, but the size of this type of memory device is greatly increased, because the connections of data lines and the number of elements are increased, as explained later in more detail.